Despite recent treatment advances, osseous complications after renal transplantation remain a clinically important barrier to successful rehabilitation of many patients. Afflicting 10-20% of recipients, osteonecrosis [ON] is second only to osteoporosis as the most common post-transplant skeletal complication and usually affects femoral heads. Symptomatic femoral head ON is almost always serious, accounting for considerable disability and often leads to total hip arthroplasty. Considerable uncertainty remains about the incidence, modifiable risk factors, pathogenesis, natural history, and management of this disorder. This pilot study will characterize the development and natural history of ON in renal allograft recipients and determine associated epidemiologic and clinical risk factors. The hypotheses of the study are: [1] 20% of renal transplant recipients will develop femoral head ON within 6 months post-transplant; [2] Compared to unaffected recipients, those with ON will have received higher cumulative doses of glucocorticoids, exhibited a greater decline in bone mineral density (BMD) and have more rapid bone turnover in this interval; and [3] more than 50% of patients with asymptomatic ON at 6 months post- transplant will show progressive disease, as demonstrated by magnetic resonance imaging [MRI], that will be associated with a significant decline in health-related quality of life. Fifty adult recipients of first-time renal allografts, whose standard immunosuppressive regimen includes long-term glucocorticoids will be respectively monitored for development of ON, changes in bone mass and metabolism in the early post-transplant interval. Glucocorticoid dose, markers of bone turnover (NTX, osteocalcin), metabolic diseases (PTH, calcitriol), BMD of the lumbar spine and hip, radiographs and MRI of the femoral head for ON, and responses to quality-of-life questionnaires will be examined at transplantation and at 6 months. Patients with ON at 6 months will undergo repeat MRI at 18 months post-transplant. Knowledge grained from this study will lead to future prevention, epidemiological, and basic investigators of ON.